Generally, a H-steel crossbeam is widely used for supporting floor or slab acting as the ceiling of each story of a building. That is to say, as shown in FIG. 1, a H-steel crossbeam 12 and a slab 11 configure a slab structure 10.
Meanwhile, the height of each story of the building is equal to the sum of the height of a room space and the height of the slab structure 10. That is to say, as the height of the slab structure 10 is reduced, the height of each story may be decreased. Thus, as the height of the slab structure 10 is small, the height of a story is reduced in spite of the same story number, thereby reducing a construction cost.
The height H of the slab structure 10 is equal to the sum of the height H1 of a H-steel crossbeam 12 and the height H2 of a slab 11. If the height H1 of the H-steel crossbeam 12 or the height H2 of the slab 11 is decreased to reduce the height H of the slab structure 10, the slab structure 10 becomes weaker in its supporting force or bending resistance, which influences on the safety of the structure. Here, the reference numeral 11a designates a steel bar installed to the slab 11.
In addition, if the size of the H-steel crossbeam 12 is decreased to reduce the height H of the slab structure 10, the sectional area of the H-steel crossbeam is also decreased, thereby making the H-steel crossbeam weakened against a compressing force and a bending momentum.
In order to solve the above problems, a method for installing a deck plate 14 having a groove 14a corresponding to an upper flange 12a of the H-steel crossbeam 12 to the H-steel crossbeam 12, and then placing concrete thereto to make a slab structure 15, as shown in FIG. 2, was proposed.
The slab structure 15 advantageously reduces its height as much as the depth of the groove 14a. This slab structure 15 may effectively endure the stress applied in a vertical direction A to the slab 13, but regarding the stress applied in a direction B parallel to the slab 13, a shear stress and a bending momentum are greatly concentrated in a region near the groove 14a since the thickness of the slab 13 is small in the region, and also the slab structure 15 is weak against a compressing force.
FIG. 3 is a sectional view showing a slab structure 19 including a stand 16 welded to a web 12b of the H-steel crossbeam 12, and a deck plate 17 installed to the stand 16. That is to say, the slab structure is configured in a way of welding the stand 16 to the web 12b for installation, installing the deck plate 17 on the stand 16, and then placing concrete thereto so that a predetermined portion of the H-steel crossbeam 12 is buried in the concrete.
This slab structure 19 is structurally stable in comparison to the slab structure of FIG. 2. However, the slab structure 19 is disadvantageous in that a process for welding the stand 16 to the web 12b is additionally required, and the structure may have seriously bad stability if the welding portion between the stand 16 and the web 12b is not firm.
In addition, in the above slab structures, H-steel is weak against fire since it is exposed outward. That is to say, high temperature caused by the fire may be directly transferred to the H-steel, which may cause deformation of the H-steel. In order to prevent this problem, the exposed H-steel should be coated with heat-resisting material.
Meanwhile, when constructing beams and slabs in the conventional art, H-steel is connected between columns, and then a mold is installed to surround them. Thus, it causes delay of construction process and economic loss in installing the mold and also removing the mold after casting.